Ramdisk is fast because it is not a disk at all, it is just fas-access memory. All the data in memory, including the ramdisk, is lost every time you reboot your computer. Totally, irretrievably lost.
Duplicati2 is able to recreate the job-specific databases, but it cannot recreate for you the database that holds the database settings. It is not a big task to redefine the jobs, but any log information that was attached to them is also lost with the database.
For any files you want to keep on disk, you need a HDD or SSD. Ramdisk is for temporary storage only.